Towards Best Practices in Clinical Magnetoencephalography: Patient Preparation and Data Acquisition

Abstract

A magnetoencephalography (MEG) recording for clinical purposes requires a different level of attention and detail than that for research. As contrasted with a research subject, the MEG technologist must work with a patient that may not fully cooperate with instructions. The patient is on a clinical schedule, with generally no opportunity to return due an erroneous or poor acquisition. The data will generally be processed by separate MEG analysts, who require a consistent and high-quality recording in order to complete their analysis and clinical report.To assure a quality recording, (1) MEG technologists must immediately recheck their scalp measurement data during the patient preparation, in order to catch disturbances and ensure registration accuracy of the patient fiducials, electrodes, and head position indicator (HPI) coils. During the recording, (2) the technologist must ensure that the patient remains quiet and as far in as possible in the helmet. After the recording, (3) the technologist must consistently prepare the data for subsequent clinical analysis.This paper aims to comprehensively address these matters for practitioners of clinical MEG in a helpful and practical way. Based on the authors' experiences in recording over three thousand patients between them, presented here are a collection of techniques for implementation into daily routines that ensure good operation and high data quality. The techniques address a gap in the clinical literature addressing the multitude of potential sources of error during patient preparation and data acquisition, and how to prevent, recognize, or correct those.

Indications for Inpatient Magnetoencephalography in Children – An Institution’s Experience

“…Furthermore, a number of devices will typically accompany any patient requiring intensive care, including portable ventilators and other monitors that can be the source of considerable competing magnetic noise. Such artifacts must be adequately processed during and after recordings with the use of the tSSS method (Burgess, 2020;Mosher and Funke, 2020). The cases presented in this paper do, however, demonstrate that such technical aspects can be overcome, and good quality data can be obtained in critically ill patients in an acute, inpatient setting.…”

“…Simultaneous EEG was recorded using a 22-channel electrode array already placed in the hospital setting [pediatric intensive care unit (ICU) or epilepsy monitoring unit (EMU)], except in one case where only pre-surgical functional mapping was performed without EEG electrodes. Before recording, the positions of three external fiduciary points, five head position indicator coils, all EEG electrodes, and several hundred head shape points were obtained (Mosher and Funke, 2020). During all recordings, continuous head position monitoring was performed to account for any shift in head position.…”

Good Scientific Practice in MEEG Research: Progress and Perspectives

“…Unlike highly-motivated research volunteers, however, patients present their own confounds and contaminants that must be accounted for. More recently, (Mosher & Funke, 2020) provided practical guidelines for the preparation of MEG patients and instruments for routine clinical operations. Here we review key points of the clinical MEG exam, with reference to these other publications for explicit details.…”

“…Commercial MEG arrays are arranged in rigid helmet configurations, which rely on the HPI coils to determine the location of the patient within this helmet space, and thus the HPI coils must be accurately located in the patient's coordinate system. In all cases, the proper use of a 3D stylus is an art in itself, and therefore technicians must be trained and cross-checked in its use (Mosher & Funke, 2020).…”

“…Although perhaps obvious, we are surprised in clinical practice to review data sets where the patient was allowed to "slump" out of the helmet, such that brain coverage by the MEG sensors is incomplete. Recovery of data from cortical locations outside of the helmet is nearly impossible, and therefore the patient must be monitored throughout the recording to ensure that they remain as deep in the helmet as possible (Mosher & Funke, 2020).…”